1. Field of the Invention
The present invention relates to a web-fed rotary printing press capable of rapid production changes having several double printing units. Each individual printing unit of the double printing unit has a form cylinder and a transfer cylinder. The transfer cylinders of the individual printing units are adjustable with respect to each other for printing both sides of a web that is fed through the double printing unit by the blanket--blanket method.
2. Description of the Related Art
Referring to FIG. 9, a known prior art printing press 10 is shown for printing on both sides of a web 9. In this prior art printing press 10, four double printing units 1, 2, 3, and 4 are used to print four colors on each side of the web 9, which is designated as the printing of 4+4 colors. To change the production in this printing press, each of the double printing units 1 through 4 must be stopped. Printing plates in each printing unit are changed for the new production while the entire printing press is stationary. If plate-change aids are not installed in the printing units, the web 9 must also be cut. Changing production requires completely stopping the printing press which results in a corresponding loss of time. Initial spoilage during a restart of the printing press is unavoidable. Although not shown, it is obvious that each of the individual printing units of the double printing units 1 through 4 may include its own drive for rotating its cylinders.
A prior art European reference, EP 0644048 A2, discloses a printing press in which a first printing unit containing a form cylinder and a transfer cylinder cooperates alternately with a similar second or third printing unit in the blanket--blanket method. Each of the printing units has its own drive motor. A change in production can be effected without interrupting the travel of the web, but only one printed image on one web side can be changed at one time.
Another prior art reference, Swiss Patent 549 471, discloses a web-fed rotary printing press with double printing units arranged alongside of each other which, operating by the blanket--blanket method, prints a web which is passed between the transfer cylinders. For changing production, individual printing units are selectively connectable and disconnectable. In the disconnected position, the transfer cylinders of the double printing units are separated by a distance allowing the web to pass through the double printing unit without touching the transfer cylinders. The transfer cylinders are mounted in levers by which they can be swung around a corresponding form cylinders to disconnected the double printing unit. The swinging is effected against spring force by toggle levers acting on the journals of the transfer cylinders.
Similar prior art double printing units which can be selectively operated are shown in German reference DE 44 35 429 A1. In this reference, double printing units are arranged one above the other and work together with a roll changer of adjustable width and with a displaceable folding apparatus. In this reference, the transfer rollers of each double printing unit are selectively separable for changing print productions.